1. Technical Field
The present disclosure relates in general to a processing system, and more particularly to monitoring alignment of a stage in the processing system and the related calibration targets and stages.
2. Background Art
Utilization of optical metrology in semiconductor manufacturing has grown significantly over the past several years. The technology provides capabilities to conduct measurements of a wide variety of critical device parameters, including, for example, critical dimensions, depths and sidewall angles. The benefits of optical metrology include non-invasive and fast measurement capabilities with relatively low cost of ownership. The non-contact characteristic of the optical metrology is of great value because any time a contact is made to the surface of a device there is a possibility that the device could be damaged and/or contaminated. For optical metrology tools to yield measurement results that are matched, it is necessary that the optical metrology tools produce well defined incident light beams, and properly collect reflected light beams for analysis.
One critical parameter for an optical metrology measurement is the angle of incidence (AOI) of the produced light beam. AOI is often considered a fixed parameter in the majority of the optical metrology techniques. The AOI is characterized through a system calibration procedure which is accessed by the recipe/library during the calculations of the measurement results. Preferably prior to AOI characterization and calibration, stage alignment needs to be monitored and stage tilt (if any) needs to be corrected.